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SEC'iIOMSIX Soil-Bentonlte Cutoff Wail Marsh funnel viscosity and mud-balance density tests were performed on the slurry immediately after mixing. The slurry was then hydrated for approximatelytwenty-four hours. After hydrating, the slurry was again mixed and the viscosity and density of the cured slurry were measured. A filter press test was also conducted on the hydrated slurry approximately 7 days after initial mixing. The viscosity, density, and filtration results of the slurry are presented in Table 6.2.1. The laboratory test data is also included in Appendix D. A filtrate loss screening was then performed on the slurry with tap water and groundwater as the penneants to provide a rapid preliminary evaluation of the bentonite compatibility with the site water. The results of the filtrate loss test are presented graphically in Figure 6-1. No significant ' difference in the filter cake response was noted between the site ground water and tap waters, which indicates that no major degradation of the bentonite is expected due to the site groundwater. Soil-Bentonite Mix Testing Soil-bentonite backfill mixture test specimens were prepared by adding the 36 marsh-second bentonite slurry described above to the composite soil samples to achieve an estimated six-inch slump. This resulted in approximately 2.26% bentonite being added in the form of slurry to Composite No. 1.52% to Composite No. 3, and 1.02% to Composite No. 4. The slump, unit weight, and permeability of each backfill mix was then measured in accordance with the procedures described above. Results of the permeability testing of the three composite samples are summarized in Table 6.2.2 below. Laboratory test data and summary sheets are also included in Appendix D. 6.3 TECHNICAL SPECIFICATIONS FOR SOIL-BENTONITE CUTOFF WALL The proposed soil-bentonite cutoff wall specifications are presented in Appendix E. The technical specifications describe the construction of a permanent continuous, homogeneous, minimum 2.5 foot wide soil bentonite cut-off wall with a hydraulic conductivity of 1 x 10-~ cm/sec or less, a depth up to 55 feet below grade, and keyed a minimum distance of 4 feet into the siltstone/claystone bedrock unit. 6.4 CONSTRUCTION QUALITY CONTROLICONSTRUCTION QUALITY ASSURANCE The technical specifications presented in Appendix E include requirements for Contractor Quality Control Testing in Paragraph 3.8 and requirements for Engineer (Third Party) Quality Assurance Testing in Pazagraph 3.9 N*:\PR~OJECCT$@2238240_PLATTE_SAND_GRAVEL\SUB_OOV2.0_WORD PROC\PLATTESANDBGRAVELGEOTECHNICALDESIGNREPORT4.OD000bNOV-0S\ 6-3 V~